The Raider's offensive tackle, Mario Henderson waits for his turn in a play drill at the Oakland Raiders training camp in Napa, Calif. on Friday, July 31, 2009.
Photo by Kat Wade / Special to the Chronicle

Photo: Kat Wade, Special To The Chronicle

The Raider's offensive tackle, Mario Henderson waits for his turn...

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Raider's offensive tackle, Mario Henderson runs a play drill with the offensive line during the Oakland Raiders training camp in Napa, Calif. on Friday, July 31, 2009.
Photo by Kat Wade / Special to the Chronicle

Raiders newcomer Khalif Barnesis out for six-to-eight weeks with a broken left ankle, which means his training camp in Napa is done. That makes incumbent Mario Henderson the starting left tackle when the season starts Sept. 14 against the Chargers.

It also means Cornell Green has a safer hold on the right tackle job. Barnes was a candidate to move to the right side if Henderson held on to his starting job.

"It was going good," Barnes said of the budding fight for the right to protect quarterback JaMarcus Russell's blindside. "We had a good thing going on but this break happened."

Barnes went down in a heap during practice Tuesday morning. He was unengaged in pass protection when left guard James Martenknocked defensive tackle Ryan Boschettiinto Barnes' left knee.

The knee got a contusion, but Barnes knew right away the ankle injury was far worse.

"I told the trainers, 'I think my ankle's broken,' " said Barnes, who will wear a hard cast in lieu of surgery. "I've broken a few bones before and it starts warming up, you feel a sharp pain."

Erik Pearswill double as the backup left and right tackle. The Raiders also re-signed offensive tackle Seth Wand, who spent last season as a Raiders reserve.

Barnes, a four-year starter in Jacksonville, signed a one-year, $1.2 million contract with the Raiders in the offseason. Raiders coach Tom Cableexpects him to return early in the regular season to add depth.

More hurts: Starting cornerbacks Nnamdi Asomugha (hip flexor) and Chris Johnson(knee) are both out with strains that were described as minor.

Special teams ace Isaiah Ekejiuba (shoulder) and nose tackle Gerard Warren (illness) also sat out as the injuries piled up in the first days of contact workouts.

Briefly: The Raiders released undrafted rookie Chris O'Neill, a Miramonte High-Orinda graduate who was converted from tight end to linebacker. ... The defense continues to mix it up under new defensive coordinator John Marshallwith a variety of stunt and zone blitzes. Rookie defensive end Matt Shaughnessyskied high for a pass deflection downfield. "That's my basketball skills coming out," he said.